System for and method of manufacturing reduced iron

ABSTRACT

A system for manufacturing reduced iron includes: an injection well for supplying oxidizing gas to a coal bed existing in an underground area; a gasification region of the coal bed, in which coal gasification is performed by using the oxidizing gas; a production well for conveying coal gas aboveground, the coal gas being generated by the coal gasification; and a reducing furnace for reducing iron oxide to reduced iron by using the coal gas as reducing gas. The reducing furnace is disposed directly above or near the production well.

TECHNICAL FIELD

The present invention relates to a system for and a method of manufacturing reduced iron.

BACKGROUND ART

As a new ironmaking process without the use of a blast furnace, there is a known technique of obtaining direct reduced iron (DRI) by reducing iron ore by use of, for example, natural gas or reformed gas obtained by reforming the natural gas.

Coal gas that is generated when coal is gasified contains the same kinds of reduction components (CO, H₂) as those contained in the natural gas or the reformed gas. Accordingly, there is also a proposed method of manufacturing direct reduced iron, in which steam coal, which is less expensive than raw material coal for coke making, is gasified by a gasification furnace, and a resultant coal gas is used as reducing gas (see Patent Literature 1 and 2, for example).

CITATION LIST Patent Literature

PTL 1: Japanese Laid-Open Patent Application Publication No. S56-105411

PTL 2: Japanese Laid-Open Patent Application Publication No. 2004-169074

SUMMARY OF INVENTION Technical Problem

However, there is still room for improvement in the above conventional art examples in terms of efficiency in the manufacturing of reduced iron from iron oxide by using coal gas as reducing gas.

Each aspect of the present invention has been made in view of the above, and an object of the present invention is to provide a system for and a method of manufacturing reduced iron, both of which make it possible to improve efficiency in the manufacturing of reduced iron compared to the conventional art when manufacturing the reduced iron from iron oxide by using coal gas as reducing gas.

Solution to Problem

A system for manufacturing reduced iron according to one aspect of the present invention includes: an injection well for supplying oxidizing gas to a coal bed existing in an underground area; a gasification region of the coal bed, in which coal gasification is performed by using the oxidizing gas; a production well for conveying coal gas aboveground, the coal gas being generated by the coal gasification; and a reducing furnace for reducing iron oxide to reduced iron by using the coal gas as reducing gas. The reducing furnace is disposed directly above or near the production well.

A method of manufacturing reduced iron according to another aspect of the present invention includes: supplying oxidizing gas to a coal bed in an underground area; performing coal gasification in the coal bed by using the oxidizing gas to generate coal gas; leading the coal gas to an aboveground reducing furnace; and reducing iron oxide to reduced iron by using the coal gas as reducing gas in the reducing furnace.

Advantageous Effects of Invention

The system for and the method of manufacturing reduced iron according to the respective aspects of the present invention make it possible to improve efficiency in the manufacturing of reduced iron compared to the conventional art when manufacturing the reduced iron from iron oxide by using coal gas as reducing gas.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows one example of a system for manufacturing reduced iron according to one embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS Background that has LED to Embodiment of Present Invention

There are coal resources that have not been minable by conventional mining methods due to technological or economical reasons. In recent years, a particular technique has been drawing attention, in which such conventionally unminable coal is gasified underground. This technique makes effective utilization of coal resources possible. Such underground coal gasification (UCG) is a technique of gasifying the coal of an underground coal bed in its original position to generate coal gas, such as hydrogen gas and carbon monoxide gas. Specifically, an injection well is dug in the ground to reach the coal bed deep underground (e.g., to the depth of 1000 m or more), and oxidizing gas (such as air or oxygen gas) is supplied through the injection well. In this manner, the coal is gasified at a high temperature in the underground coal bed. The gas generated as a result of the coal gasification is conveyed aboveground through a production well.

In this respect, the inventor of the present invention has found that, when manufacturing reduced iron from iron oxide, using the coal gas obtained by the above-described UCG technique as reducing gas is significantly advantageous.

Specifically, a system for manufacturing reduced iron according to a first aspect of the present invention includes: an injection well for supplying oxidizing gas to a coal bed existing in an underground area; a gasification region of the coal bed, in which coal gasification is performed by using the oxidizing gas; a production well for conveying coal gas aboveground, the coal gas being generated by the coal gasification; and a reducing furnace for reducing iron oxide to reduced iron by using the coal gas as reducing gas. The reducing furnace is disposed directly above or near the production well.

According to the above configuration, efficiency in the manufacturing of the reduced iron can be improved by disposing the reducing furnace, in which the reduced iron is manufactured from the iron oxide, directly above or near the production well.

A method of manufacturing reduced iron according to a second aspect of the present invention includes: supplying oxidizing gas to a coal bed in an underground area; performing coal gasification in the coal bed by using the oxidizing gas to generate coal gas; leading the coal gas to an aboveground reducing furnace; and reducing iron oxide to reduced iron by using the coal gas as reducing gas in the reducing furnace.

According to the above configuration, the coal gas obtained by the UCG technique is used as the reducing gas, and thereby the reduced iron can be efficiently manufactured from the iron oxide.

In a method of manufacturing reduced iron according to a third aspect of the present invention, which is based on the method of manufacturing reduced iron of the second aspect, an impurity generated due to the coal gasification remains in the coal bed, and is separated from the coal gas, such that release of the impurity to the reducing furnace is suppressed.

There is a possibility that, during the coal gasification process, impurities generated due to the coal gasification (e.g., CO₂, sulfur components, zinc components, etc.) remain in the coal bed in the underground area, and are separated from the coal gas. Therefore, it is considered that the impurities can be removed efficiently. That is, with the UCG technique, for example, the coal gas can be obtained in a manner with less CO₂ emission, which is environmentally friendly.

As described above, at the time of the coal gasification, impurities can be removed from the coal gas more adequately compared to the conventional art. For example, CO₂ generated due to the coal gasification can be suppressed from being released to the reducing furnace. This makes it possible to eliminate or simplify a separator (gas purifying equipment) that separates the impurities generated due to the coal gasification (e.g., CO₂, sulfur components, zinc components, etc.) from the coal gas. As a result, the cost of manufacturing reduced iron can be reduced compared to the conventional art.

Hereinafter, specific examples of one embodiment of the present invention are described with reference to the drawings. It should be noted that the present invention is not limited to the specific examples of the embodiment described below.

Apparatus Configuration

FIG. 1 shows one example of a system for manufacturing reduced iron, the system adopting a method of manufacturing reduced iron according to the embodiment of the present invention.

As shown in FIG. 1, a reduced iron manufacturing system 100 of the present embodiment includes: a UCG plant 10; and a reducing furnace 20 and a separator 30 (gas purifying equipment), which are disposed on the ground 14.

The UCG plant 10 includes an injection well 11, a coal bed 12 in an underground area 15, and a production well 13.

The injection well 11 is a well for supplying oxidizing gas from an oxidizing gas supply device (not shown) to the coal bed 12 existing in the underground area 15. The oxidizing gas may be any kind of gas, so long as the gas can cause the coal of the coal bed 12 to be oxidized (combusted). It should be noted that the oxidizing gas in the description herein means a gas containing components that can cause the coal to be oxidized (combusted). Examples of the oxidizing gas include air, oxygen gas, and so forth.

When the coal bed 12 is supplied with the oxidizing gas and water, oxidization (combustion) and gasification occur on the surface of the coal bed 12. Specifically, heat is generated from oxidization (combustion) of the coal, and carbon (C) and steam (H₂O) react with each other in a high-temperature gasification region 12A of the coal bed 12. As a result, coal gas containing hydrogen (H₂), carbon monoxide (CO), etc., is generated. It should be noted that the coal of the coal bed 12 is not necessarily high grade coal, but may be low grade coal (e.g., brown coal).

At this time, there is a possibility that, during the coal gasification process, impurities generated due to the coal gasification (e.g., CO₂, sulfur components, zinc components, etc.) remain in the coal bed 12 in the underground area 15, and are separated from the coal gas. The depth of the coal bed 12 is set to such a depth that the CO₂ gas remaining in the coal bed 12 will not be discharged to the outside air above the ground 14. For example, the depth of the coal bed 12 may be 1000 m or more.

The production well 13 is a well for conveying the coal gas generated by the coal gasification above the ground 14.

It should be noted that, as described below, in the present embodiment, the coal gas is used as reducing gas for reducing iron oxide. The coal gas may be any kind of coal gas, so long as the coal gas can be used as reducing gas for reducing iron oxide. Examples of the coal gas include hydrogen gas, carbon monoxide gas, and so forth.

The UCG technique as described above has an advantage in that the UCG technique makes it possible to effectively utilize unutilized coal resources, such as high-sulfur coal, high-ash coal, steeply dipping coal beds, etc. The UCG technique is also seen as a promising technique from the viewpoints of environmental protection and global warming prevention, because, for example, this technique prevents combustion ash from being discharged above the ground 14, and reduces CO₂ generation compared to a case where the coal oxidization (combustion) and gasification are performed above the ground 14.

The separator 30 is connected to the production well 13 via suitable piping. Accordingly, the coal gas from the production well 13 flows into the separator 30. Then, the separator 30 separates the impurities generated due to the coal gasification (e.g., CO₂, sulfur components, zinc components, etc.) from the coal gas. The separator 30 may be configured in any form, so long as the separator 30 is capable of separating the impurities generated due to the coal gasification (e.g., CO₂, sulfur components, zinc components, etc.) from the coal gas. For example, as shown in FIG. 1, the separator 30 may be disposed directly above or near the production well 13. Alternatively, the separator 30 may be disposed at a suitable position in the underground area 15. The impurities separated by the separator 30 may be reused or returned to the underground area 15. It should be noted that since the separator 30 has a known internal configuration, the description of the internal configuration is omitted.

The reducing furnace 20 reduces iron oxide to reduced iron by using the above coal gas as reducing gas. In the present embodiment, the reducing furnace 20 is disposed directly above or near the production well 13. The reducing furnace 20 is connected to the separator 30 via suitable piping. Accordingly, the coal gas from the separator 30 flows into the reducing furnace 20. In the description herein, the aforementioned term “near” means that the coal gas lifted above the ground 14 through the production well 13 will not be transported over a long distance by a pipeline or the like.

In the present embodiment, the reduced iron is obtained through, for example, the following ironmaking process: an iron-oxide-containing raw material (an iron oxide material) produced from lump iron ore or pulverized iron ore is subjected to direct reduction using the reducing gas at a lower temperature than in the case of using a blast furnace. The reducing furnace 20 may be configured in any form, so long as the reducing furnace 20 is capable of reducing iron oxide to reduced iron by using the reducing gas. Examples of a gas-based direct reduction process in which iron oxide is reduced to iron by using the reducing furnace 20 include the Midrex process. The above iron oxide material may be produced not only from high-grade iron ore, but also from low-grade iron ore (e.g., iron ore containing about 30% Fe).

Operation

Hereinafter, one example of the method of manufacturing reduced iron according to the embodiment of the present invention is described with reference to FIG. 1.

First, oxidizing gas is supplied to the coal bed 12 in the underground area 15. Specifically, by using the injection well 11, the oxidizing gas such as air or oxygen gas is supplied from the oxidizing gas supply device (not shown) on the ground 14 to the coal bed 12 existing in the underground area 15.

Then, the coal of the coal bed 12 is gasified in the coal bed 12 by using the above oxidizing gas. Specifically, heat is generated from oxidization (combustion) of the coal, and carbon (C) and steam (H₂O) react with each other in the high-temperature gasification region 12A of the coal bed 12. As a result, coal gas containing hydrogen (H₂), carbon monoxide (CO), etc., is generated.

Next, the coal gas is led to the separator 30 and the reducing furnace 20 on the ground 14 sequentially in this order. Specifically, by using the production well 13, the coal gas containing hydrogen (H₂), carbon monoxide (CO), etc., is led from the coal bed 12 in the underground area 15 to the separator 30, and then the coal gas is further led to the reducing furnace 20 from the separator 30.

In this manner, impurities generated due to the coal gasification (e.g., CO₂, sulfur components, zinc components, etc.) are separated from the coal gas by using the separator 30. It should be noted that there is a possibility that, during the coal gasification process, the impurities remain in the coal bed 12 in the underground area 15, and are separated from the coal gas. Therefore, the impurities can be removed efficiently.

Next, in the reducing furnace 20, iron oxide is reduced to reduced iron by using the above coal gas as reducing gas. For example, an iron oxide material produced from lump iron ore or pulverized iron ore is used as an iron-oxide-containing raw material, and the iron oxide material is fed into the reducing furnace 20, which has been heated to a predetermined temperature. Meanwhile, since the reducing gas is introduced into the reducing furnace 20, the iron oxide material comes into contact with the reducing gas, and thereby a reduction reaction of the iron oxide progresses. As a result, direct reduced iron (DRI) pellets are produced.

Thereafter, the reduced iron pellets are, for example, conveyed into an electric furnace or the like (not shown), and after being subjected to melting, impurity removal, component adjustment, etc., go through continuous casting, rolling, and so forth. As a result, an iron product is obtained.

As described above, according to the present embodiment, efficiency in the manufacturing of reduced iron can be improved compared to the conventional art when manufacturing the reduced iron from iron oxide by using coal gas as reducing gas. For example, efficiency in the manufacturing of the reduced iron can be improved by disposing the reducing furnace 20, in which the reduced iron is manufactured from the iron oxide, directly above or near the production well 13.

Moreover, at the time of the coal gasification, impurities (e.g., CO₂, sulfur components, zinc components, etc.) can be removed from the coal gas more adequately compared to the conventional art. To be more precise, there is a possibility that the impurities generated due to the coal gasification remain in the coal bed 12 in the underground area 15, and are separated from the coal gas. Accordingly, in the present embodiment, CO₂ generated due to the coal gasification can be suppressed from being released to the separator 30 and the reducing furnace 20. This makes it possible to eliminate or simplify the separator 30 (gas purifying equipment), which removes CO₂. As a result, the cost of manufacturing reduced iron can be reduced compared to the conventional art.

INDUSTRIAL APPLICABILITY

The system for and the method of manufacturing reduced iron according to respective aspects of the present invention make it possible to improve efficiency in the manufacturing of reduced iron compared to the conventional art when manufacturing the reduced iron from iron oxide by using coal gas as reducing gas. Therefore, these aspects of the present invention are applicable to, for example, a system for and a method of manufacturing reduced iron from iron oxide by using coal gas as reducing gas.

LIST OF REFERENCE CHARACTERS

-   -   10 UCG plant     -   11 injection well     -   12 coal bed     -   12A gasification region     -   13 production well     -   14 ground     -   15 underground area     -   20 reducing furnace     -   30 separator

-   100 reduced iron manufacturing system 

1. A system for manufacturing reduced iron, comprising: an injection well for supplying oxidizing gas to a coal bed existing in an underground area; a gasification region of the coal bed, in which coal gasification is performed by using the oxidizing gas; a production well for conveying coal gas aboveground, the coal gas being generated by the coal gasification; and a reducing furnace for reducing iron oxide to reduced iron by using the coal gas as reducing gas, wherein the reducing furnace is disposed directly above or near the production well.
 2. A method of manufacturing reduced iron, comprising: supplying oxidizing gas to a coal bed in an underground area; performing coal gasification in the coal bed by using the oxidizing gas to generate coal gas; leading the coal gas to an aboveground reducing furnace; and reducing iron oxide to reduced iron by using the coal gas as reducing gas in the reducing furnace.
 3. The method of manufacturing reduced iron according to claim 2, wherein an impurity generated due to the coal gasification remains in the coal bed, and is separated from the coal gas, such that release of the impurity to the reducing furnace is suppressed. 